1. Field of the Disclosure
The present invention relates to a product having a functional layer and a method for fabricating the same, and more particularly to, a product having a functional layer with anti-corrosive, hydrophilic and anti-bacteria functions and a method for fabricating the same.
2. Discussion of the Related Art
It has been necessary in various industries, and especially in the HVAC industry, to form and use a layer having a specific function on the surface of a substrate material. Such a functional layer enhances or provides additional properties to the substrate material. For example, a functional layer having anti-corrosion and hydrophilic functions is typically formed on a surface of a heat exchanger, a surface of a side-mirror for a vehicle and the like. A functional layer formed on a heat exchanger for an air conditioner is an embodiment specifically addressed below.
An air conditioner is an electric appliance capable of controlling and providing a predetermined and desired temperature and humidity in a room. An air conditioner is typically designed to use a freezing cycle and the freezing cycle is conducted by employing a compressor, an evaporator, an expansion valve and a condenser. The evaporator and the condenser may be used as a heat-exchanger and each of these components includes a tube configured to allow refrigerant to flow therethrough, with a cooling fin installed in the tube. Heat in the ambient air is exchanged with the refrigerant flowing in the evaporator and the condenser. The evaporator absorbs the heat of the ambient air while the refrigerant is evaporating and the condenser exhausts the heat into ambient air while the refrigerant is condensing.
However, if the surface temperature of the heat exchanger falls below the dew point of the ambient air, condensation occurs and droplets are generated on the surface of the heat exchanger. Under more severe conditions, the droplets freeze and frost is formed. The droplets and/or frost generated on the surface of the heat exchanger might cause several problems. For example, droplets and/or frost would decrease the heat-exchanging area and the heat-exchanging performance of the heat exchanger could deteriorate. In addition, the droplets and frost will require an increase in the power of the fan used for air flow toward the heat exchanger, because droplets and frost are pneumatic-resistant. As a result, it is preferable that droplets are not condensed, and frost is not formed, on the surface of the heat exchanger. In order to address these problems, attempts have been made to enhance the hydrophilicity of the heat exchanger so that droplets condensed on the surface fall away.
In addition to the above a heat exchanger installed in an indoor unit or an outdoor unit may be exposed to outdoor elements. Because of this, corrosion can occur over time. This corrosion may become severe if the heat exchanger is installed in an environment containing much salt, such as near the shore of a salt water body, such as an ocean. As a result, it has been proposed to coat a corrosion-proof material on the surface of the heat exchanger.
In addition, over time fungi, bacteria and the like might inhabit the surface of the heat exchanger and generate an unpleasant odor, as well as cause sanitary problems. Since the heat exchanger is commonly installed in an indoor unit or outdoor unit, it is also not easy to keep the heat exchanger clean. Because of this, it has been proposed to form a coating having anti-bacteria and anti-fungus properties (hereinafter an “anti-bacteria coating”) on the surface of the heat exchanger.
To solve the above problems, it has been proposed to coat a functional layer on the surface of the heat exchanger. For example, chrome (Cr+6) anti-corrosive treatment is performed on the surface of the heat exchanger to make the surface corrosion-proof and a silicate coating is then formed on the surface to give hydrophilicity properties to the surface. The surface of the heat exchanger may have anti-corrosion and hydrophilicity according to one method. Such a method is typically referred to as the “PCM” method, wherein “PCM” refers to “Pre-Coated Material”. However, the PCM method has the disadvantage of ‘aging’ which deteriorates the hydrophilicity properties gradually, as time passes.
To solve the disadvantage of the PCM method, it has been proposed to coat titanium on the surface of the heat exchanger and one of these methods using titanium is disclosed in Korean Patent Application No. 10-2006-32564. In order to obtain the hydrophilic surface, a titanium coating is formed on the surface of the heat exchanger by using a plasma reaction. Since the evaporation point of titanium is thousands of degrees, it is difficult to use elemental titanium in the plasma reaction. Because of this, a titanium precursor compound that is more easily used in a plasma reaction is employed. Previously, Titanium isopropoxide (Ti(OC3H7)4) was used as a titanium precursor. In this case, hexamethyldisiloxane (HMDSO) was coated before the titanium coated layer was formed, resulting in corrosion-proof properties. Thus, titanium isopropoxide was employed as a titanium precursor for plasma deposition in order to achieve hydrophilicity.
Also, in order to obtain anti-bacteria properties, materials known to exhibit anti-bacteria properties, such as copper, cobalt and the like, were used to form precursors for plasma deposition. Consequently, in the conventional art, separate coatings for each of the anti-corrosion, hydrophilicity and anti-bacteria properties were sequentially formed to obtain the final desired layer on the heat exchanger.